Opening the prosecution's case, Deputy Public Prosecutor Nicholas Lai said the boy would testify that he was relieving himself inside a cubicle at the park toilet when Chua barged in and performed oral sex on him. The boy pushed Chua away and ran off, taking a taxi to his biological father's home.

That evening, he went to KK Women's and Children's Hospital on his own as he felt unwell.

Meanwhile, the boy's mother had filed a missing persons report at about 1.35pm that day. That evening, she received a call from the hospital and rushed there with the boy's stepfather.

The mother then reported the alleged sexual assault to the policeman who was assigned the missing persons case.

Chua was arrested on Jan 31.

DPP Lai told the court that Chua's DNA was found on the boy's boxer shorts and the door handle of the toilet. Two palm prints lifted from the door handle also matched Chua's left palm.

If convicted of sexual assault by penetration, Chua could be jailed for between eight and 20 years. He cannot be caned as he is above 50 years of age.